Flat Tube for Microchannel Heat Exchanger and Microchannel Heat Exchanger

ABSTRACT

The disclosure provides a flat tube for a microchannel heat exchanger and the microchannel heat exchanger, and relates to the field of air conditioners. The flat tube includes a first wallboard ( 1.1 ) and a second wallboard ( 1.2 ) that are formed separately; and the first wallboard ( 1.1 ) and/or the second wallboard ( 1.2 ) have/has a plurality of protrusion portions protruding into a refrigerant circulation cavity, to form multiple refrigerant channels arranged along a length direction of the flat tube. The flat tube for the microchannel heat exchanger uses a stamping method, thus reducing a production cost and a production difficulty.

TECHNICAL FIELD

The disclosure relates to the field of air conditioners, and inparticular to a flat tube for a microchannel heat exchanger and themicrochannel heat exchanger.

BACKGROUND

At present, an air-cooled heat exchanger mainly involves in acopper-tube and aluminum-fin heat exchanger and an all-aluminummicrochannel heat exchanger. In recent years, along with a continuousrise of a copper price, the copper-tube and aluminum-fin heat exchangerhas been suffered challenges from more congeneric products, while theall-aluminum microchannel heat exchanger has been increasingly favoredby the industry because of the price advantage, and is being graduallyexpanded from the field of automobile air conditioners to the field ofhousehold air conditioners and commercial air conditioners. However, amicrochannel porous flat tube in the conventional art uses amelting-extruding process mostly, and an aluminum ingot needs to bemolten secondarily, so the energy consumption is large, the cost is highand the technical threshold is high. Moreover, a flat tube extrudedformation process in the conventional art makes the flat tube be of alinear structure merely. For a structure of a nonlinear heat exchanger,it is necessary to bend a core of the heat exchanger, which results inproblems of easy extrusion, blocking, cracking and the like of a hole onthe flat tube. In a reference document having the application No.“201611225638.0”, a multichannel special-shaped flat tube is disclosed.The flat tube is formed by bending an aluminum plate for multiple times.Such a process solves the problems of large energy consumption, highcost, high technical threshold and the like of the extruded formation.But in a bending process, there are problems that a microchannel of theflat tube is blocked easily, a bending position is cracked easily, etc.

SUMMARY

In order to sore the above-mentioned problems, some embodiments of thedisclosure provides a novel flat tube for a microchannel heat exchanger,to reduce a production cost and a production difficulty.

To achieve the above objective, the disclosure uses the followingtechnical solutions.

An embodiment of the disclosure, a flat tube for a microchannel heatexchanger includes a first wallboard and a second wallboard that areformed separately, the first wallboard is connected to the secondwallboard to form a refrigerant circulation cavity, and the firstwallboard and/or the second wallboard have/has a plurality of protrusionportions protruding into the refrigerant circulation cavity to formmultiple refrigerant channels, arranged along a length direction of theflat tube, in the refrigerant circulation cavity.

In an exemplary embodiment, the protrusion portions includes a firstprotrusion and a second protrusion, the first protrusion protrudes fromthe first wallboard to the second wallboard, the second protrusionprotrudes from the second wallboard to the first wallboard, and thefirst protrusion and the second protrusion are abutted against eachother and connected; or the protrusion portions includes a firstprotrusion and a second protrusion, the first protrusion protrudes fromthe first wallboard to the second wallboard, the second protrusionprotrudes from the second wallboard to the first wallboard, the firstprotrusion is connected to the second wallboard, the second protrusionis connected to the first wallboard, and the first protrusion and thesecond protrusion are distributed in a staggered manner.

In an exemplary embodiment, the first wallboard is recessed into therefrigerant circulation cavity to form the first protrusion, the secondwallboard is recessed into the refrigerant circulation cavity to formthe second protrusion, and the first protrusion and the secondprotrusion are 0.3 mm-1.0 mm high.

In an exemplary embodiment, the first wallboard and the second wallboardare the same in structure.

In an exemplary embodiment, the protrusion portions protrudes from thefirst wallboard to the second wallboard, and the protrusion portions isconnected to the second wallboard; or the protrusion portions protrudesfrom the second wallboard to the first wallboard, and the protrusionportions is connected to the first wallboard.

In an exemplary embodiment, the protrusion portions protrudes from thefirst wallboard to the second wallboard, and the protrusion portions isconnected to the second wallboard; or the protrusion portions protrudesfrom the second wallboard to the first wallboard, and the protrusionportions is connected to the first wallboard.

In an exemplary embodiment, the protrusion portions is formed byrecessing the first wallboard into the refrigerant circulation cavity,or the protrusion portions is formed by recessing the second wallboardinto the refrigerant circulation cavity, and the protrusion portions is0.5 mm-1.2 mm high.

In an exemplary embodiment, there are multiple first protrusions andmultiple second protrusions, any of three adjacent first protrusions ofthe multiple first protrusions on the first wallboard or any of threeadjacent second protrusions of the multiple second protrusions on thesecond wallboard form an included angle

$\theta = {2\; \arctan \frac{Lv}{Lh}}$

along a refrigerant flowing direction, where the Lv is a distancebetween two adjacent first protrusions of the multiple first protrusionsalong a width direction of the first wallboard or two adjacent secondprotrusions of the multiple second protrusions along a width directionof the second wallboard, and the Lh is a distance between the twoadjacent first protrusions along a length direction of the firstwallboard or the two adjacent second protrusions along a lengthdirection of the second wallboard.

In an exemplary embodiment, the included angle θ is 60°-150°.

In an exemplary embodiment, when the protrusion portions is of atruncated cone-shaped, a top diameter Di of the protrusion portions anda bottom diameter Do of the protrusion portions meet: Do=Di+2*d*tan α,the α being a draft angle of the protrusion portions.

In an exemplary embodiment, the draft angle is 10°-25°.

In an exemplary embodiment, there are multiple protrusion portions, themultiple protrusion portions are distributed at intervals along a lengthdirection of the flat tube in the refrigerant circulation cavity, so asto form, between adjacent protrusion portions of the multiple protrusionportions, a space for allowing mutual circulation of a refrigerant inadjacent refrigerant channels.

In an exemplary embodiment, the first wallboard has a first groovesinking towards a direction away from the second wallboard, the secondwallboard has a second groove sinking towards a direction away from thefirst wallboard, and a sidewall of the first groove is connected to asidewall of the second groove to form the refrigerant circulationcavity.

In an exemplary embodiment, the sidewall of the first groove extends outof the first groove to form a first turnup, the sidewall of the secondgroove extends out of the second groove to form a second turnup, and thefirst turnup and the second turnup are connected to each other.

In an exemplary embodiment, the sidewall of the first groove and thesidewall of the second groove are at least partially overlapped to eachother, and an overlapped portion is fixed by welding.

In an exemplary embodiment, the first wallboard has a groove sinkingtowards a direction away from the second wallboard, a sidewall of thegroove extends out of the groove to form a turnup, and the turnup isconnected to the second wallboard; or the second wallboard has a groovesinking towards a direction away from the first wallboard, a sidewall ofthe groove extends out of the groove to form a turnup, and the turnup isconnected to the first wallboard.

In an exemplary embodiment, a thickness of the first wallboard and athickness of the second wallboard are 0.2 mm-0.8 mm.

In addition, an exemplary embodiment of the disclosure further disclosesa microchannel heat exchanger, which includes the above-mentioned flattube.

In an exemplary embodiment, the microchannel heat exchanger is of astraight panel shape, a circular shape, a square shape, an L shape, a Ushape or a V shape.

With the adoption of the above technical solutions, the disclosure hasthe following advantages.

1. According to the flat tube for the microchannel heat exchangerdisclosed by the disclosure, a wallboard forms, a refrigerantcirculation cavity, and a protrusion formed by recessing the wallboardforms a microchannel for flowing a refrigerant. Such a structure may usea stamping-pressing formation technology. Compared with existing porousflat tube extruded formation, the stamping-pressing technology issimple, low in energy consumption, and low in technical threshold; and aheat exchanger producer may make a selection to independently produce orpurchase it, thus reducing a purchasement cost of the flat tube andimproving a pricing power.

2. The flat tube for the microchannel heat exchanger disclosed by thedisclosure uses the stamping-pressing formation technology, so differentmolds may be designed to stamp a material, to form the microchannel flattube having multiple internal structures. Compared with the existingporous flat tube extruded formation, the structure is flexible, theprocess is simple, and the reliability is high; and meanwhile, with thestamping formation, a bending operation turns out to be unnecessary, andthe problems that the microchannel of the flat tube is easily blockedand cracked and the like in the bending operation are prevented.

3. The flat tube for the microchannel heat exchanger disclosed by thedisclosure may be provided as a form in which two wallboards aresymmetrical, so the two wallboards may be machined completely just byopening the mold once. Therefore, the production step is simplified, themold opening expense is reduced, and the production cost is saved.

4. According to the flat tube for the microchannel heat exchangerdisclosed by the disclosure, a turnup and a protrusion are in solderingconnection, so the process is simple and reliable, and the sealingproperty is good; meanwhile, as the protrusion is connected to thewallboard, or connected to the protrusion, and a soldering process isused at a junction, the protrusion may bear a high pressure of therefrigerant; and by virtue of the soldering connection, a position ofthe protrusion may be prevented from being impacted by a high-pressurerefrigerant to deform. Therefore, the reliability of the flat tube isimproved, and the connection strength between the two wallboards is alsoenhanced.

5. According to the flat tube for the microchannel heat exchangerdisclosed by the disclosure, since a space is provided between theprotrusions in a length direction of the flat tube, a cavity of the flattube is of a space structure to implement turbulent flowing in the tubemore easily. Compared with an existing linear hole flat tube, the heatexchange in the tube may further be enhanced.

6. According to the flat tube for the microchannel heat exchangerdisclosed by the disclosure, the wallboard forms the inward protrudingprotrusion by stamping, so a concave pit is arranged on a surface of theflat tube inevitably. Because of the concave pit, a channel is providedbetween a fin and the flat tube certainly due to incomplete welding. Ina working condition of an evaporator and a heat pump, the heat exchangertends to be installed vertically; and condensing water is gathered underthe action of the gravity and flows down via the concave pit, toimplement water drainage of the microchannel evaporator; and thus, theheat exchange efficiency is further improved.

7. When a height of each of multiple first protrusions and a height ofeach of multiple second protrusions are smaller than 0.3 mm, a crosssection of a microchannel formed by them in the flat tube is very small;and in a welding process, the refrigerant channel is blocked by awelding flux easily, so that the refrigerant flows unsmoothly in theflat tube and the heat exchange efficiency is affected. When the heightof the first protrusion and the height of the second protrusion aregreater than 1.0 mm, because of excessively large heights of theprotrusions, a degree of stretching the wallboard is higher, resultingin that the strength of the material is weakened and it is difficult tobear the pressure of the refrigerant. By the same reasoning for a thirdprotrusion, when a height of the third protrusion is smaller than 0.5mm, a cross section of a microchannel formed by the third protrusion andthe first wallboard or the second wallboard in the flat tube is verysmall; and in a welding process, the refrigerant channel is blocked bythe welding flux easily, so that the refrigerant flows unsmoothly in theflat tube and the heat exchange efficiency is affected. When the heightof the third protrusion is greater than 1.2 mm, because of theexcessively large height of the protrusion, a degree of stretching thewallboard is higher, resulting in that the strength of the material isweakened and it is difficult to bear the pressure of the refrigerant.Meanwhile, if the first wallboard and the second wallboard areexcessively thick, the stamping is more difficult; and if the firstwallboard and the second wallboard are excessively thin, both cannotbear the pressure of the refrigerant. Therefore, a thickness of 0.2mm-0.8 mm is selected. In addition, the disclosure further discloses amicrochannel heat exchanger, which includes the above-mentioned flattube.

The beneficial effects achieved by the microchannel heat exchanger arethe same as those of the above described flat tube, and will not beelaborated repeatedly herein by virtue of a similar derivative process.

These features and advantages of the disclosure will be disclosed indetail in the following specific embodiments and accompanying drawings.Preferred embodiments or means of the disclosure are described in detailin combination with the accompanying drawings but are not intended toform a limit to the technical solutions of the disclosure Additionally,these features, elements and components in the following description andaccompanying drawings mean multiple features, elements and components.For the convenience of representation, different symbols or figures aremarked, and all indicate a component having a same or similar structureor function.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure is further described below in combination with theaccompanying drawings.

FIG. 1 is a schematic diagram of Embodiment 1 of the disclosure.

FIG. 2 is a top view of Embodiment 1 of the disclosure.

FIG. 3 is a schematic diagram of a first wallboard in Embodiment 1 of hedisclosure.

FIG. 4 is a schematic diagram of a pressure angle in Embodiment 1 of thedisclosure.

FIG. 5 is a cross-sectional view of Embodiment 1 of the disclosure.

FIG. 6 is a cross-sectional view of Embodiment 2 of the disclosure.

FIG. 7 is a cross-sectional view of Embodiment 3 of the disclosure.

FIG. 8 is a cross-sectional view of Embodiment 4 of the disclosure.

FIG. 9 is a schematic diagram of Embodiment 8 of the disclosure.

FIG. 10 is a schematic diagram of Embodiment 9 of the disclosure.

FIG. 11 is a schematic diagram of Embodiment 10 of the disclosure.

FIG. 12 is a schematic diagram of Embodiment 11 of the disclosure.

FIG. 13 is a schematic diagram of Embodiment 12 of the disclosure.

FIG. 14 is a schematic diagram of Embodiment 13 of the disclosure.

IN THE FIGURES

1.1-first wallboard, 1.2-second wallboard, 1.3-first protrusion,1.4-second protrusion, 1.5-first turnup, 1.6-second turnup1.7-collection tube, 1.8-fin, 1.9-baffle plate, and 1.10-connectiontube;

2.1-first wallboard, 2.2-second wallboard, 2.3-third protrusion,2.4-first turnup, and 2.5-second turnup;

3.1-first wallboard, 3.2-second wallboard, 3.3-first protrusion,3.4-second protrusion, and 3.5-third turnup; and

4.1-first wallboard, 4.2-second wallboard, 4.3-third protrusion, and4.4-third turnup.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The technical solutions in the embodiments of the disclosure areexplained and described below in combination with the accompanyingdrawings in the embodiments of the disclosure. However, the followingembodiments are merely preferred embodiments, rather than allembodiments, of the disclosure All other embodiments obtained by aperson of ordinary skill in the art based on the embodiments of thedisclose without creative efforts shall pertain to the protection scopeof the disclosure.

Reference throughout this specification to “an embodiment” or “instance”or “example” means that a particular feature, structure orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the disclosure. The appearances of thephrase “in an embodiment” in various places throughout thisspecification are not necessarily referring to the same embodiment ofthe disclosure.

In the description of the embodiments of the disclosure, orientation orposition relationships indicated by the terms “upper”, “lower”, “left”,“right”, “horizontal”, “vertical”, “inner”, “outer”, etc. are based onthe orientation or position relationships as shown in the drawings, forease of the description of the disclosure only, rather than indicatingthat the disclosure must be constructed and operated in a particularorientation. Therefore these terms, should not be understood as alimitation to the disclosure.

Embodiment 1

The embodiment provides a microchannel heat exchanger. As shown in FIG.1 to FIG. 5, a microchannel heat exchanger includes a first wallboard1.1 and a second wallboard 1.2 that are formed separately; and the firstwallboard 1.1 and the second wallboard 1.2 are opposite to each other,with a thickness t of 0.2 mm. The first wallboard 1.1 sinks towards adirection away from the second wallboard 1.2 to form a first groove (notlabeled in the figure), the second wallboard 1.2 sinks towards adirection away from the first wallboard 1.1 to form a second groove (notlabeled in the figure), and the first groove and the second groove forma refrigerant circulation cavity. First protrusions 1.3 are disposed onthe first wallboard 1.1. Second protrusions 1.4 are disposed on thesecond wallboard 1.2. Each of the first protrusions 1.3 is of atruncated cone-shaped and may also be of a strip shape and other shapes.In this embodiment, each of the first protrusions 1.3 is of thetruncated cone-shaped preferably and uniformly distributed on a bottomwall of the first groove. Each of the second protrusions 1.4 is of thetruncated cone-shaped, and uniformly distributed on a bottom wall of thesecond groove. In this embodiment, a height d of each of the firstprotrusions 1.3 and a height d of each of the second protrusions 1.4 are0.3 mm. A top diameter Di of each of the first protrusions 1.3 and a topdiameter Di of each of the second protrusions 1.4 are 0.8 mm-1.5 mm, anda bottom diameter Do=Di+2*d*tan α, where the α is a draft angle for thefirst protrusions 1.3 and the second protrusions 1.4. In thisembodiment, the draft angle α is 10°-25°. In this way, on one hand, aproblem of poor circulation of a refrigerant due to an excessively smallchannel in a flat tube may be prevented to improve the heat exchangeefficiency; and on the other hand, by means of a reasonable design of atop diameter, a bottom diameter and a draft angle of a protrusion, aconnection strength of a wallboard may be guaranteed, and thus a firstprotrusion and a second protrusion can bear a large pressure of therefrigerant after being connected.

In this embodiment, two sidewalls of the first groove extend out of thefirst groove to form two first turnups 1.5, and two sidewalls of thesecond groove extend out of the second groove to form two second turnups1.6. In this embodiment, the first protrusions 1.3 and the first turnups1.5 are formed by stamping the first wallboard 1.1, and the secondprotrusions 1.4 and the second turnups 1.6 are formed by stamping thesecond wallboard 1.2. Compared with the existing porous flat tubeextruded formation, the stamping-pressing technology is simple, low inenergy consumption and low in technical threshold; and a heat exchangerproducer may make a selection to independently produce or purchase it,thus reducing a purchasement cost of the flat tube and improving apricing power. Meanwhile, in different use occasions, different moldsmay be designed according to different working conditions to stamp thewallboard, to form the microchannel flat tube having multiple internalstructures to be suitable for different demands. Compared with theexisting porous flat tube extruded formation, the structure is flexible,the process is simple, and the reliability is high; and meanwhile, withthe stamping formation, a bending operation turns out to be unnecessary,and the problems that the microchannel of the flat tube is easilyblocked and cracked and the like in the bending operation are prevented.The first protrusions 1.3 and the second protrusions 1.4 are the same inshape, quantity and position, and the first turnups 1.5 and the secondturnups 1.6 are the same in shape and position. As a result, the firstwallboard 1.1 and the second wallboard 1.2 are symmetrical. The twowallboards may be machined completely just by opening a mold once.Therefore, the production step is simplified, the mold opening expenseis reduced, and the production cost is saved. The first wallboard 1.1 isconnected to the second wallboard 1.2, the two first turnups 1.5 are insoldering connection with the two turnups 1.6, and a top surface of eachof the first protrusions 1.3 is in soldering connection with a topsurface of each of the second protrusions 1.4, so the process is simpleand reliable, and the sealing property is good. Meanwhile, the topsurface of the first protrusions 1.3 and the top surface of the secondprotrusions 1.4 are abutted against each other and also in solderingconnection, so that the first protrusions 1.3 and the second protrusions1.4 may bear a high pressure of the refrigerant By virtue of thesoldering connection, the first protrusions 1.3 and the secondprotrusions 1.4 may be prevented from being impacted by a high-pressurerefrigerant to deform. Therefore, the reliability of the flat tube isimproved, and the connection strength between the first wallboard 1.1and the second wallboard 1.2 is also enhanced.

As shown in FIG. 4, there are multiple first protrusions and multiplesecond protrusions, an included angle formed by any of three adjacentfirst protrusions of the first protrusions 1.3 on the first wallboard orany of three adjacent second protrusions of the second protrusions onthe second wallboard along a flow direction of the refrigerant isdefined as an incoming-flow pressure angle θ,

${\theta = {2\; \arctan \frac{Lv}{Lh}}},$

where the Lv is a distance between two adjacent first protrusions of themultiple first protrusions along a width direction of the firstwallboard or two adjacent second protrusions of the multiple secondprotrusions along a width direction of the second wallboard, and the Lhis a distance between the two adjacent first protrusions along a lengthdirection of the first wallboard or the two adjacent second protrusionsalong a length direction of the second wallboard. The incoming-flowpressure angle θ has an impact on a tube-pass pressure drop and the heatexchange efficiency. In this embodiment, the incoming-flow pressureangle θ may be 60°-150°. In actual applications, an appropriateincoming-flow pressure angle may be selected as required by the heatexchange efficiency. For example, when a high heat exchange efficiencyis required, a large incoming-flow pressure angle should be used, suchas θ=90°-150°, to improve the heat exchange efficiency by means ofincreasing a pressure drop. Reversely, for a demand having a restrictionon the pressure drop, a small incoming-flow pressure angle should beused, such as θ=60°-90°.

Additionally, a strength factor φ is defined to represent apressurization behavior of a tube pass of the flat tube. The φ isaffected by the distance Lv between two adjacent protrusions along thewidth direction of the wallboard, the distance Lh between two adjacentprofusions along the length direction of the wallboard, and the topdiameter Di of the protrusion, specifically,

$\phi = {\frac{2*{Lv}*{Lh}}{\pi^{*}{Di}^{2}}.}$

In this embodiment, in order to guarantee the connection strength of thewallboard, the φ is 13-20.

For an assembled flat tube, on a length direction, the protrusionportions are formed by multiple first protrusions 1.3 and multiplesecond protrusions 1.4 by soldering connection forms multiplerefrigerant channels in a refrigerant circulation cavity formed by thefirst groove and the second groove. As each of the first protrusions 1.3and each of the second protrusions 1.4 are of the truncated cone-shaped,a space for allowing the refrigerant in adjacent refrigerant channels tocirculate to each other forms between adjacent protrusion portions ofthe multiple protrusion portions. Consequently, a cavity of the flattube is of a space structure, which is easier to implement turbulentflowing in the tube. Compared with an existing linear hole flat tube,the heat exchange in the tube may further be enhanced.

The first protrusions 1.3 and the second protrusions 1.4 are formed bystamping, so a panel surface of the first wallboard 1.1 and a panelsurface of the second wallboard 1.2 sink into the refrigerantcirculation cavity to form multiple concave pits. Because of the concavepits, a plurality of channels are provided between a fin and the flattube certainly due to incomplete welding In a working condition of anevaporator and a heat pump, the heat exchanger tends to be installedvertically; and condensing water is gathered under the action of thegravity and flows down via the concave pit, to implement water drainageof the microchannel evaporator; and thus, the heat exchange efficiencyis further improved.

Embodiment 2

As shown in FIG. 6, different from Embodiment 1, a microchannel heatexchanger in this embodiment includes a first wallboard 2.1 and a secondwallboard 2.2 that are formed separately; and the first wallboard 2.1and the second wallboard 2.2 are opposite to each other. In thisembodiment, the first wallboard 2.1 and the second wallboard 2.2 have athickness t of 0.2 mm. The first wallboard 2.1 sinks towards a directionaway from the second wallboard 1.2 to form a first groove, the secondwallboard 2.2 sinks towards a direction away from the first wallboard2.1 to form a second groove, and the first groove and the second grooveform a refrigerant circulation cavity. Multiple third protrusions 2.3are disposed on the first wallboard 2.1. Each of the third protrusions2.3 is of a truncated cone-shaped and is uniformly distributed on abottom wall of the first groove. In this embodiment, a height d of eachof the third protrusions 2.3 is 0.5 mm. Two sidewalls of the firstgroove extend out of the first groove to form two first turnups 2.4, andtwo sidewalls of the second groove extend out of the second groove toform two second turnups 2.5. In this embodiment, the third protrusions2.3 and the two first turnups 2.4 are formed by stamping the firstwallboard 2.1, the second turnups 2.5 are formed by stamping the secondwallboard 2.2, the two first turnups 2.4 are in soldering connectionwith the two second turnups 2.5, and a top surface of each of the thirdprotrusion 2.3 is in soldering connection with a plate surface of thesecond wallboard 2.2.

Embodiment 3

As shown in FIG. 7, different from Embodiment 1, a microchannel heatexchanger in this embodiment includes a first wallboard 3.1 and a secondwallboard 3.2 that are formed separately; and the first wallboard 3.1and the second wallboard 3.2 are opposite to each other. In thisembodiment, the first wallboard 3.1 and the second wallboard 3.2 have athickness t of 0.8 mm. The first wallboard 3.1 sinks towards a directionaway from the second wallboard 3.2 to form a first groove, the secondwallboard 3.2 is a flat plate, multiple first protrusions 3.3 aredisposed on the first wallboard 3.1, multiple second protrusions 3.4 aredisposed on the second wallboard 3.2, each of the first protrusion 3.3is of a truncated cone-shaped and is uniformly distributed on a bottomwall of the first groove, each of the second protrusion 3.4 is also ofthe truncated cone-shaped, and each of the second protrusion 3.4 andeach of the first protrusion 3.3 are the same in shape, quantity andposition. In this embodiment, a height d of each of the firstprotrusions 3.3 and a height d of each of the second protrusions 3.4 are1.0 mm. Two sidewalls of the first groove extend out of the first grooveto form two third turnups 3.5. In this embodiment, the first protrusions3.3 and the third turnups 3.5 are formed by stamping the first wallboard3.1, the second protrusions 3.4 are formed by stamping the secondwallboard 1.2, the third turnups 3.5 are directly in solderingconnection with a plate surface of the second wallboard 3.2, and a topsurface of the first protrusions 3.3 are in soldering connection with atop surface of the second protrusions 3.4.

Embodiment 4

As shown in FIG. 8, different from Embodiment 1, a microchannel heatexchanger in this embodiment includes a first wallboard 4.1 and a secondwallboard 4.2 that are formed separately; and the first wallboard 4.1and the second wallboard 4.2 are opposite to each other. In thisembodiment, a thickness t of the first wallboard 4.1 and a thickness tof the second wallboard 4.2 are 0.6 mm. The first wallboard 4.1 sinkstowards a direction away from the second wallboard 4.2 to form a firstgroove. The second wallboard 4.2 is a flat plate. Multiple thirdprotrusions 4.3 are disposed on the first wallboard 4.1. Each of thethird protrusions 4.3 is of a truncated cone-shaped and is uniformlydistributed on a bottom wall of the first groove. In this embodiment, aheight d of each of the third protrusions 4.3 is 1.2 mm. Two sidewallsof the first groove extend out of the first groove to form two thirdturnups 4.4. In this embodiment, the third protrusions 4.3 and the thirdturnups 4.4 are formed by stamping the first wallboard 4.1, the thirdturnups 4.4 are directly in soldering connection with a plate surface ofthe second wallboard 4.2, and a top surface of each of the thirdprotrusions 4.3 is in soldering connection with a plate surface of thesecond wallboard 4.2.

Embodiment 5

Different from Embodiment 1, in this embodiment, a thickness of a firstwallboard and a thickness of a second wallboard are 0.4 mm; multiplefirst protrusions are disposed on the first wallboard; multiple secondprotrusion are disposed on the second wallboard; both each of the firstprotrusions and each of the second protrusions are of a truncatedcone-shaped; a height of each of the first protrusions is 1.0 mm, with atop surface of each of the first protrusions in soldering connectionwith the second wallboard; a height of each of the second protrusion is1.0 mm, with a top surface of each of the second protrusions insoldering connection with the first wallboard; and the first protrusionsand the second protrusions are arranged in a staggered manner, to formmultiple refrigerant channels arranged along a length direction of aflat tube.

Embodiment 6

Different from Embodiment 1, in this embodiment a thickness of a firstwallboard and a thickness of a second wallboard are 0.5 mm, and a heightof each of multiple first protrusions and a height of each of multiplesecond protrusions are 0.8 mm. A sidewall of the first groove and asidewall of the second groove are at least partially overlapped to eachother, and an overlapped portion is fixed by soldering connection.

Embodiment 7

Different from Embodiment 2, in this embodiment, a thickness of a firstwallboard and a thickness of a second wallboard are 0.5 mm, and a heightof each of multiple third protrusions is 1.0 mm.

Embodiment 8

As shown in FIG. 9, the embodiment provides a microchannel heatexchanger, including two collection tubes 1.7; multiple connection tubes1.10 connected to a refrigeration system are disposed on one collectiontube 1.7; multiple flat tubes described in Embodiment 1 are connectedbetween the two collection tubes 1.7; a wavy fin 1.8 is disposed betweenadjacent flat tubes to increase a heat dissipation area; and meanwhile,the fin 1.8 is also disposed on outside surfaces of two flat tubeslocated on end portions of the collection tubes 1.7, and the fin 1.8herein is protected by a baffle plate 1.9 to prevent deformation anddamage of the fin 1.8. The microchannel heat exchanger in thisembodiment is of a straight panel shape.

Embodiment 9

As shown in FIG. 10, different from Embodiment 8, a microchannel heatexchanger in this embodiment is of an L shape. The L-shaped microchannelheat exchanger is formed by bending a flat tube and a baffle plate 1.9on a length direction. A fin 1.8 is disposed between the flat tube andthe flat tube as well as between the flat tube and the baffle plate 1.9.

Embodiment 10

As shown in FIG. 11, different from Embodiment 8, a microchannel heatexchanger in this embodiment is of a U shape. The U-shaped microchannelheat exchanger is formed by bending a flat tube and a baffle plate 1.9on a length direction. A fin 1.8 is disposed between the flat tube andthe flat tube as well as between the flat tube and the baffle plate 1.9.

Embodiment 11

As shown in FIG. 12, different from Embodiment 8, a microchannel heatexchanger in this embodiment is of a V shape. The V-shaped microchannelheat exchanger is formed by bending a flat tube and a baffle plate 1.9on a length direction. A fin 1.8 is disposed between the flat tube andthe flat tube as well as between the flat tube and the baffle plate 1.9.

Embodiment 12

As shown in FIG. 13, different from Embodiment 8, a microchannel heatexchanger in this embodiment is of a circular shape. The circularmicrochannel heat exchanger is formed by bending a flat tube and abaffle plate 1.9 on a length direction. Two collection tubes of themicrochannel heat exchanger are abutted against each other to form aclosed loop. A fin 1.8 is disposed between the flat tube and the flattube as well as between the flat tube and the baffle plate 1.9.

Embodiment 13

As shown in FIG. 14, different from Embodiment 8, a microchannel heatexchanger in this embodiment is of a square shape. The squaremicrochannel heat exchanger is formed by bending a flat tube and abaffle plate 1.9 on a length direction. Two collection tubes of themicrochannel heat exchanger are abutted against each other to form aclosed loop. A fin 1.8 is disposed between the flat tube and the flattube as well as between the flat tube and the baffle plate 1.9.

The above are merely specific embodiments of the disclosure, and theprotection scope of the present disclosure is not limited thereto. Itshould be understood by the person skilled in the art that thedisclosure includes but not limited to the accompanying drawings and thecontent described in the specific embodiments. Any modification withoutdeparting from a function and a structural principle of the disclosureis included in the scope of the claims.

What is claimed is:
 1. A flat tube for a microchannel heat exchanger,comprising a first wallboard and a second wallboard that are formedseparately, wherein the first wallboard is connected to the secondwallboard to form a refrigerant circulation cavity, the first wallboardhas a plurality of protrusion portions protruding into the refrigerantcirculation cavity to form multiple refrigerant channels, arranged alonga length direction of the flat tube, in the refrigerant circulationcavity; or the second wallboard has a plurality of protrusion portionsprotruding into the refrigerant circulation cavity to form multiplerefrigerant channels, arranged along a length direction of the flattube, in the refrigerant circulation cavity; or the first wallboard andthe second wallboard both have a plurality of protrusion portionsprotruding into the refrigerant circulation cavity to form multiplerefrigerant channels, arranged along a length direction of the flattube, in the refrigerant circulation cavity.
 2. The flat tube as claimedin claim 1, wherein the protrusion portions comprises a first protrusionand a second protrusion, the first protrusion protrudes from the firstwallboard to the second wallboard, the second protrusion protrudes fromthe second wallboard to the first wallboard, and the first protrusionand the second protrusion are abutted against each other and connected;or the protrusion portions comprises a first protrusion and a secondprotrusion, the first protrusion protrudes from the first wallboard tothe second wallboard, the second protrusion protrudes from the secondwallboard to the first wallboard, the first protrusion is connected tothe second wallboard, the second protrusion is connected to the firstwallboard, and the first protrusion and the second protrusion aredistributed in a staggered manner.
 3. The flat tube as claimed in claim2, wherein a part of the first wallboard is recessed into therefrigerant circulation cavity to form the first protrusion, a part ofthe second wallboard is recessed into the refrigerant circulation cavityto form the second protrusion, and the first protrusion and the secondprotrusion are 0.3 mm-1.0 mm high.
 4. The flat tube as claimed in claim3, wherein the first wallboard and the second wallboard are the same instructure.
 5. The flat tube as claimed in claim 1, wherein theprotrusion portions protrudes from the first wallboard to the secondwallboard, and the protrusion portions is connected to the secondwallboard; or the protrusion portions protrudes from the secondwallboard to the first wallboard, and the protrusion portions isconnected to the first wallboard.
 6. The flat tube as claimed in claim5, wherein the protrusion portions is formed by recessing a part of thefirst wallboard into the refrigerant circulation cavity; or theprotrusion portions is formed by recessing a part of the secondwallboard into the refrigerant circulation cavity, and the protrusionportions is 0.5 mm-1.2 mm high.
 7. The flat tube as claimed in claim 2,wherein there are multiple first protrusions and multiple secondprotrusions, any of three adjacent first protrusions of the multiplefirst protrusions on the first wallboard or any of three adjacent secondprotrusions of the multiple second protrusions on the second wallboardform an included angle θ=2 arctan Lv/Lh along a refrigerant flowingdirection, where the Lv is a distance between two adjacent firstprotrusions of the multiple first protrusions along a width direction ofthe first wallboard or two adjacent second protrusions of the multiplesecond protrusions along a width direction of the second wallboard, andthe Lh is a distance between the two adjacent first protrusions along alength direction of the first wallboard or the two adjacent secondprotrusions along a length direction of the second wallboard.
 8. Theflat tube as claimed in claim 7, wherein the included angle θ is60°-150°.
 9. The flat tube as claimed in claim 1, wherein when theprotrusion portions is of a truncated cone-shaped, a top diameter Di ofthe protrusion portions and a bottom diameter Do of the protrusionportions meet: Do=Di+2*d*tan α, the α being a draft angle of theprotrusion portions.
 10. The flat tube as claimed in claim 9, whereinthe draft angle is 10°-25°.
 11. The flat tube as claimed in claim 1,wherein there are multiple protrusion portions, the multiple protrusionportions are distributed at intervals along a length direction of theflat tube in the refrigerant circulation cavity, so as to form, betweenadjacent protrusion portions of the multiple protrusion portions, aspace for allowing mutual circulation of a refrigerant in adjacentrefrigerant channels.
 12. The flat tube as claimed in claim 1, whereinthe first wallboard has a first groove sinking towards a direction awayfrom the second wallboard, the second wallboard has a second groovesinking towards a direction away from the first wallboard, and asidewall of the first groove is connected to a sidewall of the secondgroove to form the refrigerant circulation cavity.
 13. The flat tube asclaimed in claim 12, wherein the sidewall of the first groove extendsout of the first groove to form a first turnup, the sidewall of thesecond groove extends out of the second groove to form a second turnup,and the first turnup and the second turnup are connected to each other.14. The flat tube as claimed in claim 13, wherein the sidewall of thefirst groove and the sidewall of the second groove are at leastpartially overlapped to each other, and an overlapped portion is fixedby welding.
 15. The flat tube as claimed in claim 1, wherein the firstwallboard has a groove sinking towards a direction away from the secondwallboard, a sidewall of the groove extends out of the groove to form aturnup, and the turnup is connected to the second wallboard; or thesecond wallboard has a groove sinking towards a direction away from thefirst wallboard, a sidewall of the groove extends out of the groove toform a turnup, and the turnup is connected to the first wallboard. 16.The flat tube as claimed in claim 1, wherein a thickness of the firstwallboard and a thickness of the second wallboard are 0.2 mm-0.8 mm. 17.A microchannel heat exchanger, comprising the flat tube as claimed inclaim
 1. 18. The microchannel heat exchanger as claimed in claim 17,wherein the microchannel heat exchanger is of a straight panel shape, acircular shape, a square shape, an L shape, a U shape or a V shape.